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as you can see, i'm not a subie guy, though I've been a member on this forum for a couple of years. i run an evo 9 gsr in SM, which I'm selling to run an Evo 9 mr in STU or ASP.

the reason I'm posting here is because I'd like to start a petition to allow one of the differentials to be upgraded in STU and STX classes for AWD cars.
I'm not sure how into evos you guys are over here, but the rear diff mod has been revolutionary in terms of evo handling - it really lets you bring the car around on power.

I think it's a good chance for the SCCA to reconsider its position on aftermarket differentials for AWD cars in STU/X. As it stands right now, 2WD cars in ST are allowed to run any aftermarket differential, while AWD cars are not - this rule was originally created to handicap AWD cars, but I think that a handicap like that is unnecessary and much harder for the rules to justify. If any change is possible, now would be the best time, since our AWD cars have shown that they aren't undefeatable (see M3 for details).

This may not have as much impact on STIs, (which I believe have the R160/180 diff - which is already good), but has a definite impact on STX WRXes. There is real benefit to be had by doing this mod - one that was not commonly explored for evos until maybe 2008 or 2009.
Taking a quick glance at the Nationals results last year, WRXes seem to be more or less struggling to be competitive in this class. What the rear diff mod has allowed evos to do is optimize their setup rather than running some huge rear sway bar/other tricks to get the car to rotate, and let the rear differential take care of the corner exit. I think a WRX with this mod would be way more competitive in STU if it were able to do this mod. Drivetrain wise, the WRX doesn't really have a lot going for it - much like the 03 Evos (open front, viscous center, improperly stacked and weak to begin with rear diff) - how many 03-04 evos do you see doing well in a class that limits drivetrain modifications?

To be clear, this goes beyond restacking plates/refreshing the rear diff to factory spec. evo rear diffs were improperly stacked from the factory so that they'd be quieter, smoother, whatever. I believe mustangs with factory LSDs are set up the same way. This is more about mods that add plates and change lockup, like TRE's ($450), or beyond (Cusco, etc.)

Also to be clear, I mean open up the rules to allow one of the diffs of the car to be modified. the rest of the determination is up to individuals. i don't see this as all that outrageous of an idea

I see the evo rear diff mod as quite different than an aftermarket differential. Simply changing the internals of the evo rear diff to match the FSM is perfectly legal already. No need to add aftermarket differentials to our ST cars IMO.

Just because Evo's didn't win this year doesn't mean they should be fighting for a modification that could help in the future. They have won many times before. And if WRX's can't keep up in STX, maybe it just isn't the right car for STX

Also this will probably be moved to the autocross section of the forum if it says moved later on.

I see the evo rear diff mod as quite different than an aftermarket differential. Simply changing the internals of the evo rear diff to match the FSM is completely legal already. No need to add aftermarket differentials to our ST cars IMO.

That's not the mod I'm talking about - restacking the plates to match the FSM is what is currently done for STU evos, but I'm talking about what's offered now by TRE, Shep, etc where they actually add plates into the diff and make it a 1.5 way. Not to mention full aftermarket units like Cusco, Kaaz, etc.

Why no need for ST cars? This mod transforms the evo in classes where it is allowed. I get legitimate power oversteer on corner exit if I feel like being careless and just put my foot down. I don't think the subies do that right now. Any mod that helps WRXs catch up in STX that's allowed for those older 3 series and RX8s I would think is "needed"

::
It's not about winning STU or whatever. Just a mod that completely changes the handling of the cars and the enjoyment of them. It was to handicap AWD cars beyond the natural weight penalty, but I don't think that handicap is "necessary" anymore. This literally cures understeer in evos, I'm sure it does the same in STIs and WRXs

That's not the mod I'm talking about - restacking the plates to match the FSM is what is currently done for STU evos, but I'm talking about what's offered now by TRE, Shep, etc where they actually add plates into the diff and make it a 1.5 way. Not to mention full aftermarket units like Cusco, Kaaz, etc.

Alright. You didn't really specify the exact "rear diff mod" in the OP. I still feel the current rule set is fine and that aftermarket diffs are just another expensive expense to add to our cars that already handle very well.

Quote:

Originally Posted by kyoo

Why no need for ST cars? This mod transforms the evo in classes where it is allowed. I get legitimate power oversteer on corner exit if I feel like being careless and just put my foot down. I don't think the subies do that right now. Any mod that helps WRXs catch up in STX that's allowed for those older 3 series and RX8s I would think is "needed"

Evo's still beat the STi's quite often even if the STi's don't experience what you are talking about. I don't see it as a problem in STU specifically whatsoever. In STX I do see where you are coming from about the WRX, and it has seemed like the wrong car to have to win in STX for awhile. Yet the M3 seemed to be looked at as the wrong car to have in STU for a long time until this year when one finally won and it was blown out of proportion imo.

Quote:

Originally Posted by kyoo

::
It's not about winning STU or whatever. Just a mod that completely changes the handling of the cars and the enjoyment of them. It was to handicap AWD cars beyond the natural weight penalty, but I don't think that handicap is "necessary" anymore. This literally cures understeer in evos, I'm sure it does the same in STIs and WRXs

Thanks for the input

I like your reasoning here that I underlined more than anything else. But I am still not convinced. I like STU and ST classes how they are currently.

Again this is just my opinion and that really doesn't mean all that much

The car I want to prep for this season did not win National's; therefore we should allow an AWD specific mod that will give my car a significant advantage against M3's and people who can't afford differentials.

Now I don't know you but I can assume that's not why you're saying this. The M3 winning isn't overly impressive. I thought it was at first, that he must've been cheating or something else but from the sounds of it, the course favored the M3. Now you were saying SP class as a possible destination for your car. The only difference between STU with diff's and ASP is boost and slicks. That's taking away the general principles behind the ST classes.

I agree with Yazel in that it could potentially have it's place in STX in the form of rear LSD's to replace the open diff but in all honesty, the wrx isn't a strong front runner in STX.

Now a potential ST class modification I've wanted is sprung aftermarket clutches. I know an STU Evo 8 guy who went through 2 clutches last season which inevitably caused him to spend a lot of money and revert to the cheaper Miata. Clutches aren't expensive but really take a toll on budgets for the year.

i'll look into rewording the original OP, as i don't think it's coming off the way i'm meaning for it to.

my personal reason for wanting the rear diff is because it makes the car so much more fun, while not going too crazy on the power route. it's more or less the way the evo was designed to handle with AYC, only more natural.

i don't care that the M3 won at nationals, I don't care if it keeps winning. i just want my fellow AWD owners to be able to drive a car that kicks the rear out on power, and maybe not have to constantly be fighting the weight, understeer, etc that is typical for AWD cars. im actually glad that it won - i wouldn't have dreamt of asking for this mod if evos and stis kept winning STU every year.

For STX WRXs, I think it could make all t he difference in the world - not just for what the LSD would provide, but the way it allows you to set up the car.

i don't care that the M3 won at nationals, I don't care if it keeps winning. i just want my fellow AWD owners to be able to drive a car that kicks the rear out on power, and maybe not have to constantly be fighting the weight, understeer, etc that is typical for AWD cars.im actually glad that it won - i wouldn't have dreamt of asking for this mod if evos and stis kept winning STU every year.

Contradictory much (bolded words)? I'm just kidding and see what you mean!

I actually like that part of STU and AWD cars (underlined part). It makes the battle to win that much more fun. Everyone says our cars (AWD cars) are as simple as point and shoot, but as you stated it isn't just that simple. With the current rules we can do so much to cure those problems anyways.

I like your simple reasoning of making your car more fun though. That is what it should be about at some point.

lol i reworded the OP. it's kind of sad that it's coming off as, whiny evo owner looking for additional edge. i just think this restriction is forcing STU evo owners to miss out on some awesome power oversteer, and at the same time I guarantee it will do the same for STis and WRXs - though I think more benefit for WRXs. I think it'll also help older Evos that were especially gypped in the drivetrain department to be a little more competitive.

As far as I can tell, drivetrain-wise, the single most influential piece in terms of handling is the rear diff. just page through that rear diff thread on evom to see what i mean.

Quote:

Originally Posted by yazel

Contradictory much (bolded words)? I'm just kidding and see what you mean!

I actually like that part of STU and AWD cars (underlined part). It makes the battle to win that much more fun. Everyone says our cars (AWD cars) are as simple as point and shoot, but as you stated it isn't just that simple. With the current rules we can do so much to cure those problems anyways.

I like your simple reasoning of making your car more fun though. That is what it should be about at some point.

i didn't notice until just now. it was a, 'now that i think of it,' kind of thing.

Now I don't want to be misleading. I codrive yazel's car lol. We're not trying to team up on you over this subject but having friends who run Evo's in STU, we have these general opinions.

Yes, it'd be more fun to go out and have more oversteer. I giggle like a school girl when the tires are cold and I get tail happy; however, I autocross to win (at least I try haha) and I think the battle with understeer and everything is what makes it fun and hard to master.

The weight issue really isn't a good one to talk about. E36, Evo and STi prepped curb weights are typically in the high 30xx to 3200 lbs.

I applaud you for bringing this topic up though. Might help us address the clutch issue we're thinking of

Now I don't want to be misleading. I codrive yazel's car lol. We're not trying to team up on you over this subject but having friends who run Evo's in STU, we have these general opinions.

Yes, it'd be more fun to go out and have more oversteer. I giggle like a school girl when the tires are cold and I get tail happy; however, I autocross to win (at least I try haha) and I think the battle with understeer and everything is what makes it fun and hard to master.

The weight issue really isn't a good one to talk about. E36, Evo and STi prepped curb weights are typically in the high 30xx to 3200 lbs.

I applaud you for bringing this topic up though. Might help us address the clutch issue we're thinking of

gotcha. depending on your setup, you can still have a battle with understeer if you want just kidding. i missed what you posted about the clutches before, that's an interesting point. like i said before though, i think now is as good a time as any to call some of these rules into question - i.e., if the SCCA were starting today, starting fresh, would it again impose a stock clutch only rule? or a no aftermarket differential rule for AWD cars only? (in ST) the diff is a hard argument given how well evos and stis do, but if we were only looking at the WRX, maybe it wouldn't be.

Looks like Mike B basically has the same opinion as I do on the whole thing and Geoff doesn't see it as necessary either according to the posts in your thread on evom.

The more I think about it, this really should only be something WRX guys in STX should be worrying about. Not STU guys at all. And I know you are directing it as a benefit to AWD cars in ST classes as a whole, but it just isn't needed for all AWD cars in ST as a whole. (all of my posts in this thread sound like an echo of the last )

What all is done to your new IX so far? (beautiful car btw!!!) Why are you considering both STU and ASP? Sorry for the off topic.

lol I think we can go ahead and leave the topic

for a little history, I had a IX GSR that I kind of went wild with, doing whatever mod I wanted - ended up in SM with FP Green, full boltons, cams, GTWorx/Bilstein, WL bushings, built trans, t-case, and Cusco rear diff. After going through all that and having my fair share of problems, decided to move to a stock MR to start over - plus I always wanted white

with the new evo, going with a much more mild setup powerwise - car's got an exhaust and fmic from the original owner, totally stock motor. i'm at a point where i can go either STU or ASP, but i guess if i can only have the rear diff if I go ASP, that's what I'll do. i don't plan on running wider wheels/tires than stock, and I guess i'll go with a mbc ebcs hybrid setup since I can in ASP. the MR 6 speed has been known to be weak so I'll get it built, keep the stock t-case, and bring over the Cusco rear diff. Just ordered Ohlins DFVs which I'm stoked about, so I guess I'll go from there! It won't be a competitive car but it'll be damn fun to drive lol

::
one final on topic note though, maybe STX WRXs can still move forward with this - i still think it'd be helpful for WRXs in that class to have a little more edge at nationals.

Definitely will be fun! If you aren't worried about being competitive or running at the National level just do whatever to the car. I am sure even local STU guys wouldn't care all that much if you did the diff mod and ran STU. You would be losing power over what you probably have now for an STU legal tune as well, and I am sure it is quite mild compared to your old setup!

Also with ASP and SM having only a .001 pax difference this year you would be able to freely switch between those classes and have similar pax results if you care about pax.

Definitely will be fun! If you aren't worried about being competitive or running at the National level just do whatever to the car. I am sure even local STU guys wouldn't care all that much if you did the diff mod and ran STU. You would be losing power over what you probably have now for an STU legal tune as well, and I am sure it is quite mild compared to your old setup!

Also with ASP and SM having only a .001 pax difference this year you would be able to freely switch between those classes and have similar pax results if you care about pax.

that's what kills me - i'm almost more or less running an STU car + rear diff which bumps me into ASP, the difference between PAX in STU and ASP is huge. I do want to be somewhat competitive, but I guess it won't be in this car!

for a little history, I had a IX GSR that I kind of went wild with, doing whatever mod I wanted - ended up in SM with FP Green, full boltons, cams, GTWorx/Bilstein, WL bushings, built trans, t-case, and Cusco rear diff. After going through all that and having my fair share of problems, decided to move to a stock MR to start over - plus I always wanted white

with the new evo, going with a much more mild setup powerwise - car's got an exhaust and fmic from the original owner, totally stock motor. i'm at a point where i can go either STU or ASP, but i guess if i can only have the rear diff if I go ASP, that's what I'll do. i don't plan on running wider wheels/tires than stock, and I guess i'll go with a mbc ebcs hybrid setup since I can in ASP. the MR 6 speed has been known to be weak so I'll get it built, keep the stock t-case, and bring over the Cusco rear diff. Just ordered Ohlins DFVs which I'm stoked about, so I guess I'll go from there! It won't be a competitive car but it'll be damn fun to drive lol

::
one final on topic note though, maybe STX WRXs can still move forward with this - i still think it'd be helpful for WRXs in that class to have a little more edge at nationals.

If you have a not stock FMIC then you this whole STU discussion is a mute point.

There's only one thing that scares autoxers more than turbo cars in ST is AWD cars playing with differentials in ST.

I'm not going tell you not to try, but I will say that this is a battle that has been faught since STX and STUs inception and has constantly and completely failed to make it beyond the advisory committee.

The reasoning is that this is not a common modification street mod for AWD cars, and the costs to entry (i.e. "If they have it, I have to have it" perceptions, are too high.

And you're completely and wholly incorrect on the reason 2WD cars are allowed diffs.

Quote:

As it stands right now, 2WD cars in ST are allowed to run any aftermarket differential, while AWD cars are not - this rule was originally created to handicap AWD cars, but I think that a handicap like that is unnecessary and much harder for the rules to justify.

The allowance for 2WD cars is to level the playing field against AWD cars. Once you start allowing AWD cars to change diffs, there's nothing equivalent for 2WD cars to do. It was not to handicap AWD cars.

Not saying your proposal won't go through... just saying you may be spending a hell of a lot of time to be told... "Thank you for your comments, but no."

And then you also shot yourself in the foot with this...

Quote:

This may not have as much impact on STIs, There is real benefit to be had by doing this mod - one that was not commonly explored for evos until maybe 2008 or 2009.

You're creating an imbalance between STis and EVOs. Proposing changes to rules that only benefit a select few cars is the fastest way to be told "ain't happening" "Thank you for your comments. We do not believe this aligns with the class structure."

Adding aftermarket diff possibilities to STU would likely destroy the class, as it would add a much more complicated and expensive setup process. Besides, my car has plenty of power on oversteer if I want it. It is generally not the fastest way around a course, though...

For WRXs in STX, and STis and WRXs in STU, what would you think about opening that up to allow AWD vehicles to change/add one aftermarket LSD?

In other words:
-If you had a WRX you could swap out the rear viscous for a clutch type
-If you had an 07+ STi you could swap out the torsen for a clutch type
-If you had an Evo/04-06 STi you could just put a nicer rear diff in

Near as I can figure, this would not impact STR at all, it would make the WRX more competitive in STX but not overly so, and would probably increase the range of competitive cars in STU (the Torsen cars and the 09+ WRXs would have a better shot at things). Evo IX's and 05-06 STis are going to slowly die off, so this might set the class up better for the future.

It would likely become a must have mod for those cars though, which has a range of expensiveness, and opens up more ground for tuning. That said, STR has that problem as it sits, nothing stopping people from dropping coin on an OS Giken diff or whatever. And they are okay with it. They didn't need to make that allowance since the target cars (S2K, Miata) were available with Torsen limited slips, but they did.

If you have a not stock FMIC then you this whole STU discussion is a mute point.

would easily swap back to FMIC - i really don't care about the power

Quote:

Originally Posted by SpeedTheory

Why not just go back to a stock diff?

I don't understand the logic of "I don't want to change rear diffs, but I'm going to quadruple my tire budget to run in ASP instead".

it's not about the money or tires etc - it's about how fun the car is with the rear diff - a lot of people are nonbelievers.

Quote:

Originally Posted by KC

There's only one thing that scares autoxers more than turbo cars in ST is AWD cars playing with differentials in ST.

I'm not going tell you not to try, but I will say that this is a battle that has been faught since STX and STUs inception and has constantly and completely failed to make it beyond the advisory committee.

The reasoning is that this is not a common modification street mod for AWD cars, and the costs to entry (i.e. "If they have it, I have to have it" perceptions, are too high.

And you're completely and wholly incorrect on the reason 2WD cars are allowed diffs.

The allowance for 2WD cars is to level the playing field against AWD cars. Once you start allowing AWD cars to change diffs, there's nothing equivalent for 2WD cars to do. It was not to handicap AWD cars.

Not saying your proposal won't go through... just saying you may be spending a hell of a lot of time to be told... "Thank you for your comments, but no."

And then you also shot yourself in the foot with this... You're creating an imbalance between STis and EVOs. Proposing changes to rules that only benefit a select few cars is the fastest way to be told "ain't happening" "Thank you for your comments. We do not believe this aligns with the class structure."

--kC

not that this necessarily makes it "better," but i should mention i meant the allowance for one diff, i.e., front, rear or center - sort of like how the rule for sway bars in stock class was changed from just front bar to front or rear bar.

i should have been a little clearer - make no mistake that stis would absolutely benefit from this. i'm sure all cars will pick up a little time from a mod like this, but the majority of the benefit comes from being able to adjust the behavior of the car